Solve for $x$ and $y$ using substitution. ${-x-4y = 8}$ ${x = -5y-9}$
Explanation: Since $x$ has already been solved for, substitute $-5y-9$ for $x$ in the first equation. ${-}{(-5y-9)}{- 4y = 8}$ Simplify and solve for $y$ $5y+9 - 4y = 8$ $y+9 = 8$ $y+9{-9} = 8{-9}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -5y-9}\thinspace$ to find $x$ ${x = -5}{(-1)}{ - 9}$ $x = 5 - 9$ ${x = -4}$ You can also plug ${y = -1}$ into $\thinspace {-x-4y = 8}\thinspace$ and get the same answer for $x$ : ${-x - 4}{(-1)}{= 8}$ ${x = -4}$